Adverse cutaneous photosensitivity reactions following exposure to environmental chemicals and light have been reported with increasing frequency during recent years. The broad objective of our research is to define more precisely the underlying mechanisms of these adverse photoresponses. Our approach is to work in the interface between isolated test tube photochemical studies and the physiologic, but highly complex photobiologic responses in the whole organism. Specifically, this year our goals include: a) To chemically characterize the photoproduct(s) of protriptyline which cause red cell lysis and to study the mechanism of this lysis; b) To determine the chemical structure of the photoproducts between DNA and chlorpromazine and to determine if chlorpromazine photosensitizes DNA chain scission; c) To determine whether or not chlorpromazine and protriptyline covalently bond after irradiation to membrane proteins and, if so, does this reaction play a role in their RBC lytic ability; d) To further develop mechanistic studies of musk ambrette photoallergy and its relationship to persistent light reactivity; e) To achieve a functioning fluorescence microscope which is able to characterize excitation and emission spectra of photosensitizers in tissue samples; f) To determine the time required for repair of UV-induced pyrimidine dimer in vivo in human skin.